Expansion-bit



(No Model.)

R. H. BROWN.

EXPANSION BIT.

No. 530,923. Patented Dec. 18,1894;

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UNITED STATES PATENT OFFICE.

REUBEN H. BROWN, OF NEW'HAVEM'CONNEOTICUT.

EXPANSION-BIT.

SPECIFICATION forming part of Letters Patent No. 530,923, dated December 18, 1894.

Application filed January 23. 1894:- Serial No. 497,759. (No model.)

To aZZ whom it may concern..-

Be it known that I, REUBEN H. BROWN, a citizen of the United States, and a resident of New Haven, in the county of New Haven and State of Connecticut, have invented certain new and useful Improvements in Expansive Bits, of which the following is a specification.

My invention relates to that'class of boring bits which have an adjustable cutter, usually denominated expansible bits, it being an im-' provement on what is known in the trade as the Clark bit of which I am now the sole owner and maker, such improvement relating more particularly to Patent N 0. 141,324, dated July 29, 1873, wherein is shown a semi-cylindrical cutter-head. Heretofore, in bits of this class having adjustable cutters, it has been difficult to hold the cutter against its seat in the cutterhead so as to prevent chips working between and thus lift the cutter therefrom. To counteract this tendency as much as possible, the cutter is usually dovetailed in the cutterhead, which is an expensive operation, besides the cutter-head is materially weakened thereby. In the former case, wherein the cutter is held down entirely by the clamping plate and its screw, the entire cutting strain is brought against said screw, frequently st ripping it. In the latter construction, the cut ting strain of the bit is brought against that part of the cutter-head already weakened by the beveled undercut.

In my improvement I construct the cutterblade with a circular base and provide a correspondingly transverse circular seat in the cutter-head, so placed that the cutting strain will be in a direct line therewith, thus strengthening the said head, besides relieving the strain on the clamping screw.

To enable others to understand my invention, reference is had to the accompanying drawings, in which- Figure 1 represents a side elevation of one form of my improved cutter-head with a cutter therein having a circular base and a cutting edge arranged tangentially therewith. Fig. 2 is a side elevation of the cutter-head, the cutter, clamping plate and its screw removed therefrom. Fig.3 is a view similar to Fig.1, showing a slight change in the seat for the clamping plate on the cutter. Fig. 4

is a front elevation of the bit and broken section of the shank. Fig. 5 is an end view of the bit, looking in the direction of arrow a, Fig. 4.. Fig. 6 is an end elevation similar to Fig. 5, with cutter removed. Fig. 7 is a perspective view of the cutter shown in Figs. 1

and 4 Fig. 8 is a broken section of the cutter-head, with a modified form of my improved cutter therein whose cutting edge, while not exactly diametrical with the circular base, is set in sufficient to enable such base to project and thus form a self-sustaining seat for the said cutter. Fig. 9 is a detail end view of the cutter shown in Fig. 8.

Its construction and operation are as follows:

1 represents the cutter-head having the shank 2. This cutter-head is of a semi-cylindrical shape, as shown in Fig. 6. On the upper cut away portion (see Fig. 2) is milled the circular seat or groove 3 for the cutter and the ledge 4 for the clamping plate.

The circular seat 3 is placed far enough from the end 5 of the cutter-head 1 and the lower cylindrical portion of such head, so as to insure the necessary strength in those portions of such head and also provide the proper inclination or angle to the portion 6 which supports the knife or cutter, which angle or inclination is best suited for clearance and support of said cutter.

The cutter 7, Fig. 7, is provided with the circular base 8 adapted to [it the before-mentioned circular seat 3 of the cutter-head 1. Its inclined face bis adapted to rest (Fig. 1) against the angular face 6 (Fig. 2) of the cutter head. The cutting edge 0 of the knife or cutter 7 will, by means of its angular position, project (see also Fig. 5) beyond the edge or lip d of the cutter-head 1, which arrangement will prevent chips lodging between the said cutting edge and the end of the cutterhead. It will be observed by this arrangement of the cutter, that the cutting strain is in the direction of the arrows e and f, Figs. 1 and 3, and the resultant of such strain is equally distributed around the circular seat 3 asindicated by the arrows g, h, i, so that the cutter will: maintain close contact with the inclined seat 6 irrespective of the clampingrplate 9 and its screw 10, which, in this case, is subject to no strain whatever from the operation of the cutter, the clamping plate merely serving to prevent the lateral displacement of the cutter, or, in other words, to prevent the cutter movinglaterally in the direction as indicated by arrows j, 76, Fig. 5. By means of this peculiar construction and position of the cutter, the slightest pressure of the clamping plate will be sufficient to hold the cutter firmly against any tendency to such accidental lateral displacement.

The circular seat 3 is formed at an angle with the cutter-head so as to give a shear to the cutter, as shown in Fig. 4. The said outter is provided with the usual spur m, and these cutters may be of any length required.

The only diiference between the cutters shown in Figs. 1 and 7 and the one in Fig. 3 is the seat thereon for the clamping plate. In the former, the horizontal floor or ledge n. is provided, in connection with the inclined wall 0, against which rest the bottom and inclined faces of the said clamp; while in the arrangement shown in Fig. 3 the floor n is dispensed with, the inclined face or wall only being used. The large bearing surface provided for the cutter in its seat within the cutter-head enables it to be firmly supported against accidental transverse displacement by the slightest tension applied to the plate screw 10, as the whole tendency of such pressure is in the line of the greatest utility, as indicated by the arrow 19. The opposite edge of the clamping plate is also beveled to engage with the under-cut or bevel q of the cutfer-head, as seen at Fig. 2, thus providing a fulcrum which still further enhances the clamping facility of said plate.

The construction shown in Figs. 8 and 9 possesses all the advantages as related to the other construction before mentioned, and, in addition thereto, the circular base is extended farther around, thus enabling the projecting portion b of said base to fulfill all the requirements of the beveled undercut heretofore used, without weakening the head. This feature, combined with the seat or ledge 01 and inclined face 0, enables the cutter to be held firmly in place with but a modicum of pressure exerted by the clamping plate.

While the inclined face I) of the cutter shown in Figs. 8 and 9, is not tangential with the circular base, as in the other views, neither is it diametrical therewith, as such an arrangement would give too great an inclination to its cutting edge. I therefore hold myself at liberty to use both methods, as each is supported by a circular base, and while one face is set in toward the center of the circular base farther than the other, they should both be substantially parallel with each other.

Having thus fully described my invention, what, therefore, I claim as new is- 1. An expansible bit, comprising in combination asemi-cylindrical head having a gimlet pointed lead screw, a transverse recess formed in such head having circular foot and rear end walls, an angularly disposed front wall tangential with said circle, a cutter having a circular base to engage with the circular recess of the cutter-head, and a forward bearing surface tangential with the said circular base to engage with the angularly disposed front wall of said head, said bearing surface projecting beyond the cutter head and terminating in a cutting lip, a clamping plate and screw to prevent transverse displacement of the cutter, as set forth.

2. An expansible bit, comprising in combination, shank 2, semi-cylindrical head 1, lead screw 11, circular recess 3 angularly disposed front wall 6 tangential with said circular recess, cutter 7 having the circular base 8 to fit the circular recess of the cutter head, and the bearing surface I) tangential with said circular base, and arranged to rest against the angular front wall of the cutter-head, said bearing surface projecting beyond the end of said head and terminating in the cutting lip c and spur m, the angular disposition of the said cutter being on a line with the cutting strain, in combination with its circular base, preventing vertical displacement of said outter, clamping plate 9, ledge or floor 4: having under-cut q therefor, said plate having an inclined forward edge to rest against the inclined wall 0 of the cutter, and the base of said plate against the horizontal ledge 07. of said cutter, so as to prevent accidental transverse displacement of the cutter, all arranged as described and for the purpose set forth.

3. In a bit of the character described, the combination with the head 1, having a circular cutter seat formed transversely therein, inclined front wall to support the cutter-blade, of a cutter having a circular base, a cutterblade projecting therefrom, floor n. and incline 0 to engage the clamping plate, combined with such clamping plate and its screw, substantially as set forth.

Signed at New Haven, in the county of New Haven and State of Connecticut, this 27th day of December, A. D. 1893.

REUBEN II. BROWN.

\Vitnesses:

S. L. SQUIER, FRANK K. LOVELAND. 

